setsockopt() did not accept UDP_SEGMENTID:
GSO_FAILEDCategory: Routes and network stack Status in RKNHardering 2.10.0: Active check Role in the verdict: Low
This page describes the actual implementation in RKNHardering 2.10.0. It distinguishes what can be done without root, what requires root, and where a mitigation only reduces one signal without hiding the VPN as a whole.
The probe creates a UDP socket and attempts setsockopt(IPPROTO_UDP, UDP_SEGMENT, 1200). On failure, it emits gso_failed with the errno. The checker treats this as low-confidence informational data because lack of GSO is not considered a VPN indicator.
The kernel or libc returns an error while configuring UDP_SEGMENT.
It shows that UDP GSO is unavailable to this socket, kernel, or environment. This depends on kernel configuration and API support, not only on the VPN.
How the line affects the report: The line is informational or diagnostic. It is useful for comparing runs, but does not by itself prove the presence of a VPN or tampering.
The verdict logic does not distinguish ENOPROTOOPT, EINVAL, EPERM, or other causes. Android kernels and vendor backports vary. The physical-interface path is not tested.
This line must be evaluated together with neighboring signals. A clean result from a single API does not simultaneously cover Java Binder, libc, raw netlink/syscalls, procfs/sysfs, local sockets, and server-side indicators.
For a diagnostic signal, do not “fix” anything at first. Record a baseline on the same device without a VPN, then repeat the test with the VPN under the same network, temperature, and load conditions. Only a reproducible difference between series is useful for analysis. A single MTU, timing, or GSO value is not evidence. Record the errno and kernel version. Do not change the VPN because a kernel feature is unavailable.
A root module can change this metric, but tuning for a particular number can easily disrupt TCP/UDP, DNS, calls, or power consumption. VPNHide Next claims to filter a number of indirect parameters, but those capabilities must be tested separately from basic interface hiding. Do not enable the maximum set of kernel hooks before obtaining a clean baseline and a working rollback path. Do not load an unknown kernel module merely for UDP_SEGMENT. Support requires a compatible kernel and network stack, not a Magisk property.
adb shell uname -a
adb shell zcat /proc/config.gz 2>/dev/null | grep -E 'CONFIG_INET|CONFIG_UDP' | head -40
The exact errno is taken from the RKNHardering detail.
After any change, force-stop both RKNHardering and the VPN client, start them again, and repeat the full scan. Zygisk, Xposed, and kernel modules usually require a reboot. Compare not only this line but also neighboring signals: a partial hook often creates inconsistencies between APIs.
The probe itself runs with ordinary app permissions and does not request root. The ADB commands below are for orientation only: adb shell runs under a different UID and may see either more or less than the app process. The decisive test is to run the check again after a force-stop.
Replacing the kernel for GSO can cause a boot loop, module incompatibility, and data loss. This informational signal does not justify that risk.
Restore the stock boot/kernel image, remove the experimental module, and reboot.
Low. Verified against the UDP_SEGMENT=1200 failure branch; informational.
The status of a third-party solution does not automatically carry over to this device. A module developer’s claim is only the initial hypothesis; confirmation requires a reproducible RKNHardering result on the specific Android version, firmware, and kernel.
native_signs_probe.cpp — native probe implementation.VpnNativeDetectorChecker.kt — deep VPN verdict and confidence.NativeSignalId.kt — complete ID registry.NativeSignalCatalog.kt — category, slug, and line mapping.Related signals: gso-send-failed, gso-ok, normal-pmtu.